Ever notice how moving forward in your career comes down to networking? Eighty percent of job openings are never publicly advertised, according to a 2013 Wall Street Journal article. That makes all those business cards you’ve collected and LinkedIn connections you’ve made extremely important.

The tricky part, however, is keeping in touch with your network of former colleagues and clients in a genuine way, so you don’t come off as self-serving or stalker-like.

Part of it means maintaining some level of regular contact, so you’re never in a position where it’s been years since you’ve connected, and suddenly, in the middle of a job hunt, you have to send a sheepish "Remember me?" email.

The rest is all about reaching out in an appropriate way depending on your relationship with your contact, so you strengthen your connections and can tap them for help when you need it. Let these tips show you how to walk the line between authentic and opportunistic.

Finally, a legit reason to spend time on Facebook and LinkedIn during the workday: These and other social media sites allow you to get your name in front of old and new connections in an unobtrusive way.

As you scroll through your feed, keep an eye out for profile updates or posts from your connections.

As you scroll through your feed, keep an eye out for profile updates or posts from your connections that announce a promotion, new company direction, or a career milestone. Craft a very short post congratulating them on their achievement, along the lines of, "So excited for you" or "Way to go!" At a loss for words? Just hit the "like" button.

Cheering on your contacts on social media lets them know you stand behind them," says Dorie Clark, marketing strategy consultant and author of Stand Out Networking: A Simple and Authentic Way to Meet People on Your Own Terms. Yet you’re not asking them for anything in return and there’s no expectation of a reply. They see your name, and that puts you on their radar. You’ll also be noticed by their own contacts, and that recognition can pay off down the road.

For closer contacts, like a former mentor or key client you’ve worked with many times, don’t wait for them to post something online; some people just don’t participate in social media that way. Instead, take the initiative by sending them a regular email or message, say, every 60 days or once per quarter, suggests Clark.

The note doesn’t have to be anything more than, "How’s it going?" or an "I saw this article and thought of you" message with a link to an industry publication. The goal is to check in and get your name on their screen in a friendly, casual way.

And though it sounds a little impersonal, make it even easier to check in by using an app like Contactually or Refer.com. Both track your contacts and prompt you to reach out based on time intervals you set. Refer.com even drafts the actual text of the message for you, based on the relationship level you have with that person, so you don’t waste time searching for the right words.

Arranging for a face-to-face catch-up with each contact individually is an impractical time-suck. The solution: Set up small gatherings for a handful of people who all know each other. This way your crew of former coworkers from a past workplace, for example, can get together for a lunch or happy-hour outing.

The group get-together works for a few reasons. First, it saves everyone time and energy. Second, you avoid the discomfort that sometimes happens when you’re sitting across the table with one contact you haven’t seen in a while . . . and no longer have much to talk about.

Arranging for a face-to-face catch-up with each contact individually is an impractical time suck.

If one of your contacts taught you a valuable career lesson or helped you resolve a tricky issue, show your appreciation by sending them a note. Handwritten always comes off as more personal and meaningful. But in today’s digitally connected world, an email or social media post can be appropriate as well.

Don’t worry if they did their good deed a while ago; there’s no expiration date when it comes to praise. "I think people appreciate follow-up and kudos whenever they come, even if it’s months after the fact," says Clark. "You could write something like, ‘Thanks so much to @joesmith for the great advice on blogging a few months ago. Here’s my first post!’ He will likely be thrilled."

If someone went above and beyond, say they helped you land a new job or client, consider sending an actual gift—such as a book on their favorite subject—recommends Derek Coburn, author of Networking Is Not Working: Stop Collecting Business Cards and Start Making Meaningful Connections and CEO of Cadre, a community for business leaders. Just don’t wrap up something with your company logo on it. "That’s not a gift—it’s a promotional item," says Coburn. "Give them something small, something they can use. It’s a way to acknowledge them and say thank you."

Offering to do a business-related favor—for example, arrange an email introduction with an industry leader you know, or posting a Facebook link to a contact’s latest podcast—conveys generosity. "Most people tend to wait to network until they need something rather than reaching out authentically and genuinely," says Coburn. "Instead, take the initiative and offer to help."

Get the ball rolling by asking, "Tell me, who is your ideal client? I may know some people you should meet," suggests Coburn. Or, "What kind of investors are you looking to get on board? I’d like more clarity in case I come across an opportunity for you." Offering an assist will give you a rep as someone who is positive and wants others to thrive.

Just don’t wrap up something with your company logo on it. "That’s not a gift—it’s a promotional item."

People get promoted, marry, move away and switch specialties all the time. Keep up with all the shifts by creating a Google doc or spreadsheet that lists all your contacts by name and includes what they do and how you met—and update it every time something changes, says Clark.

By the same token, make sure any page or site that lists your professional details—your job title, company name, and contact information—also reflects your current responsibilities, so people can easily reach you and get an accurate sense of what you have done in your career and currently do, says Clark.

Staying close to business contacts means knowing when to back off. "If a colleague is really overwhelmed, it’s a nice gesture to periodically send them an email or leave a voice message and add, ‘No need to respond,’" says Clark. "This shows a lot of respect for their schedule, because they may be too busy to get back to you and likely feel guilty about it. It frees them up and lets them know you simply want to check in and show that you care."

But what if you’ve reached out several times and continue to hear crickets? Only follow up again if you have a good reason. "People are busy, so it would be foolish to write someone off if you didn’t hear back from them once or twice," says Clark. "They could be traveling or having personal issues that make it difficult to respond."

At the same time you have to accept that you might have been dumped from their network. "If they ignore three messages sent over a span of time, especially if you have particular questions in your notes, then you can assume they don’t want to keep up with you," adds Clark. Don’t sweat it—just move on.